The invention relates to improvements in friction clutches, especially for use in motor vehicles. More particularly, the invention relates to improvements in friction clutches of the type wherein a pressure plate is non-rotatably but axially movably connected to a housing or cover and is biased by one or more prestressed resilient devices (e.g., in the form of diaphragm springs) to urge a clutch plate or clutch disc against a rotary counterpressure plate (e.g., a flywheel) which is driven by the output element of an internal combustion engine in a motor vehicle. The clutch disc can serve to transmit torque to the input element of a variable-speed transmission in the power train between the engine and the wheels of a motor vehicle.
Friction clutches of the above outlined character are disclosed, for example, in published German patent application Serial No. 24 60 963, in German Pat. No. 24 41 141, in German Pat. No. 898 531 and in German Auslegeschrift No. 1 267 916.
An object of the invention is to prolong the useful life of friction clutches, particularly of friction clutches for use in motor vehicles.
Another object of the invention is to provide a friction clutch whose mode of operation is less affected by wear upon its parts than in heretofore known friction clutches.
A further object of the invention is to provide a friction clutch which can be disengaged in response to the application of a relatively small force.
An additional object of the invention is to provide a friction clutch which is constructed and assembled in such a way that the magnitude of the disengaging force need not change, or changes negligibly, irrespective of the extent of wear upon certain component parts of the friction clutch.
Still another object of the invention is to provide a simple, compact and inexpensive friction clutch which embodies the aforediscussed features.
A further object of the invention is to provide a novel and improved method of compensating for wear upon the clutch plate or clutch disc in a friction clutch of the above outlined character.
Another object of the invention is to provide a novel and improved method of compensating for wear upon the clutch disc and/or certain other component parts of a friction clutch for use in motor vehicles and the like.
An additional object of the invention is to provide the above outlined friction clutch with a novel and improved system which can automatically compensate for wear upon the friction linings forming part of the clutch disc.
Still another object of the invention is to provide a fiction clutch which exhibits the above outlined advantages and which can be assembled at a reasonable cost in automatic machines.
A further object of the invention is to provide a novel and improved aggregate which employs the above outlined friction clutch as well as one or more additional components, such as the part or parts which transmit torque to the input element and/or receive torque from the output element or elements of the friction clutch.
Another object of the invention is to provide a motor vehicle which embodies the above outlined friction clutch.
An additional object of the invention is to provide a preassembled modular engageable and disengageable aggregate which embodies the above outlined friction clutch.
Still another object of the invention is to provide a driving unit which can be used in a motor vehicle and embodies the above outlined friction clutch.
A further object of the invention is to provide a novel and improved diaphragm spring for use in the above outlined friction clutch.
Another object of the invention is to provide a novel and improved clutch plate or clutch disc for use in the above outlined friction clutch.
An additional object of the invention is to provide a novel and improved method of installing a diaphragm spring in the housing or cover of the above outlined friction clutch.
Still another object of the invention is to provide the above outlined friction clutch with novel and improved means for tiltably mounting the diaphragm spring for the pressure plate in the housing of the friction clutch.
A further object of the invention is to provide a novel and improved connection between the input element of the above outlined friction clutch and the output element of an internal combustion engine.
Another object of the invention is to provide novel and improved means for biasing the pressure plate in a friction clutch for use in motor vehicles.
An additional object of the invention is to provide friction clutch whose operation is not affected by wear (even extensive wear) upon friction linings, pressure plate and/or other parts which are subject to wear when the friction clutch is in use.
Still another object of the invention is to provide a preassembled friction clutch which can be utilized in existing motor vehicles and/or for other purposes as a superior substitute for existing friction clutches,
A further object of the invention is to provide the above outlined friction clutch with novel and improved means for opposing the bias of the diaphragm spring for the pressure plate.
Another object of the invention is to provide a novel and improved combination of friction clutch and engine for use in a motor vehicle.
One feature of the present invention resides in the provision of an engageable and disengageable torque transmitting friction clutch which can be utilized with advantage in vehicles, particularly motor vehicles. The improved friction clutch comprises a housing or cover which is rotatable about a predetermined axis, a pressure plate, means (e.g., a group of leaf springs) for non-rotatably connecting the pressure plate to the housing with limited freedom of movement in the direction of the predetermined axis, a rotary counterpressure plate (e.g., a flywheel which is driven by the output element of an engine in a motor vehicle) adjacent the pressure plate, a torque transmitting clutch disc between the two plates, and at least one resilient device reacting against the housing to bias the pressure plate toward the counterpressure plate in order to clamp the clutch disc against the counterpressure plate and to thus rotate the clutch disc about the predetermined axis. The clutch disc has friction linings which are engageable by and disengageable from at least one of the two plates and are subject to wear as a result of repeated engagement with and disengagement from the at least one plate, and the friction clutch further comprises an adjusting unit including means for compensating for wear upon the friction linings to thereby maintain the bias of the at least one resilient device upon the pressure plate at a substantially constant value, means for engaging and disengaging the friction clutch including actuating means movable along a predetermined path to engage and disengage the friction clutch, and means for varying the torque transmitted by the friction clutch and/or by the clutch disc including means for gradually reducing the transmitted torque at least during a portion of movement of the actuating means along the predetermined path to disengage the friction clutch.
The pressure plate comprises a portion which is engaged and biased by the at least one resilient device, and the disengagement of the friction clutch can involve axial movement of the pressure plate away from the counterpressure plate against the bias of the at least one resilient device. The friction clutch can further comprise means for gradually reducing the torque which is transmittable by the friction clutch at least during a portion of axial movement of the pressure plate.
The friction clutch can also comprise means for securing the housing to the counterpressure plate to thus establish a power train between the actuating means and the securing means. The torque varying means can be disposed in the power train.
The pressure plate has a friction surface which is engageable with the friction linings to establish a power train between the actuating means and the clutch disc, and the torque varying means can be disposed in such power train.
The friction linings can include a first and a second set of friction linings, and the torque varying means can be disposed axially between the two sets of friction linings.
The torque varying means can include means for axially yieldably locating at least one of the two plates and the friction linings relative to the others of the two plates and the friction linings, and the torque varying means can be acted upon by a variable force which decreases to a minimal value in response to disengagement of the friction clutch and gradually increases to a maximum value at least during a portion of movement of the actuating means along the predetermined path to engage the friction clutch.
The means for varying the torque which is transmittable by the friction clutch can include means for reducing the transmitted torque during approximately 40-70 percent of movement of the actuating means along the predetermined path in a direction to disengage the friction clutch and for gradually increasing the torque which is transmittable by the friction clutch during approximately 40-70 percent of movement of the actuating means along the predetermined path in a direction to engage the friction clutch.
The at least one resilient device (such as a diaphragm spring) can have a degressive force-to-displacement ratio at least during a portion of movement of the actuating means along the predetermined path in a direction to disengage the friction clutch.
As mentioned above, the at least one resilient device can comprise a diaphragm spring which bears against the pressure plate. The friction clutch preferably further comprises a seat which tiltably mounts the diaphragm spring in the housing. The diaphragm spring can comprise an annular portion and the actuating means can comprise prongs or tongues which extend from the annular portion of the diaphragm spring. Such prongs can be of one piece with the annular portion of the diaphragm spring. The seat can comprise two portions (e.g., in the form of wire rings) which are disposed at opposite sides of the diaphragm spring. The latter can have a substantially sinusoidal force-to-displacement characteristic curve including a maximum, a minimum, a degressive portion between the minimum and the maximum, an operating point at the degressive portion in engaged condition of the friction clutch, and a ratio of forces from approximately 1:0.4 to 1:0.7. between the maximum and the minimum.
If the friction clutch is used in a motor vehicle, the means for engaging and disengaging the friction clutch can further comprise means for moving the actuating means and such moving means can include or constitute a pedal which is similar or analogous to the gas pedal of the motor vehicle.
Another feature of the invention resides in the provision of a motor vehicle having a gas pedal, an engageable and disengageable friction clutch, means for engaging and disengaging the friction clutch including actuating means movable along a predetermined path to disengage the clutch, and means for moving the actuating means including a second pedal which is similar or analogous to the gas pedal of the motor vehicle.
An additional feature of the invention resides in the provision of a preassembled engageable and disengageable clutch assembly or aggregate which comprises a housing, a pressure plate, a counterpressure plate which is rotatable about a predetermined axis, means for non-rotatably connecting the pressure plate to the counterpressure plate with limited freedom of movement in the direction of the predetermined axis, a torque transmitting clutch disc between the two plates, at least one resilient device which reacts against the housing to bias the pressure plate toward the counterpressure plate and to thereby clamp the clutch disc between the two plates, friction linings which form part of the clutch disc and are engageable by and disengageable from at least one of the two plates so that they are subject to wear as a result of repeated engagement with and disengagement from the at least one plate, an adjusting unit including means for compensating at least for wear upon the friction linings to thereby maintain the bias of the at least one resilient device upon the pressure plate at a substantially constant value, means for engaging and disengaging the clutch aggregate or assembly including actuating means movable along a predetermined path to disengage the clutch aggregate or assembly, and means for gradually reducing the torque which is transmitted by the clutch disc during a portion of movement of the actuating means to disengage the clutch assembly or aggregate. The torque reducing means can include at least one resilient element which is in series with the at least one resilient device.
Still another feature of the invention resides in the provision of a clutch aggregate or assembly which comprises a twin-mass flywheel including a first rotary mass connectable to an output shaft of a combustion engine and a second mass rotatable relative to the first mass, an oscillation damper having means for opposing rotation of the two masses relative to each other, and a torque transmitting friction clutch including a counterpressure plate forming part of the second mass, a pressure plate, means for non-rotatably connecting the pressure plate to the counterpressure plate with limited freedom of axial movement, a torque transmitting clutch disc between the two plates, at least one resilient device acting upon the pressure plate to bias the clutch disc against the counterpressure plate, friction linings forming part of the clutch disc and being engageable with and disengageable from at least one of the two plates and being subject to wear as a result of repeated engagement with and disengagement from the at least one plate, an adjusting unit including means for compensating at least for wear upon the friction lings to thereby maintain the bias of the at least one resilient device upon the pressure plate at a substantially constant value, means for engaging and disengaging the friction clutch including actuating means movable along a predetermined path to disengage the friction clutch, and means for gradually reducing the torque which can be transmitted by the friction clutch and/or by its clutch disc during a portion of movement of the actuating means in a direction to disengage the friction clutch.
The friction clutch of the just outlined clutch aggregate or assembly can further comprise a housing and means for securing the housing to the second mass so that the housing is separable from the second mass only in response to at least partial destruction or deformation of one of the two parts including the housing and the second mass.
The clutch disc of the aforementioned clutch aggregate or assembly can be provided with at least one substantially annular friction surface and the damper can be located radially outwardly of the friction surface.
A further feature of the invention resides in the provision of a clutch aggregate or assembly for use with a combustion engines particularly in a motor vehicle. Such clutch aggregate or assembly comprises a torque transmitting friction clutch including a pressure plate, a counterpressure plate (such as a flywheel) which is rotatable about a predetermined axis, means for non-rotatably connecting the pressure plate to the counterpressure plate with limited freedom of axial movement, a torque transmitting clutch disc between the two plates, at least one resilient device acting upon the pressure plate to bias the clutch disc against the counterpressure plate, friction linings forming part of the clutch disc and being engageable with and disengageable from at least one of the two plates and being subject to wear as a result of repeated engagement with and disengagement from the at least one plate, an adjusting unit including means for compensating at least for wear upon the friction linings to thereby maintain the bias of the at least one resilient device upon the pressure plate at a substantially constant value during the useful life of the friction clutch, means for engaging and disengaging the friction clutch including actuating means movable along a predetermined path to disengage the friction clutch, means for gradually reducing the torque which can be transmitted by the friction clutch and/or by the clutch disc during a portion of movement of the actuating means in a direction to disengage the friction clutch, and axially elastic means for coupling the friction clutch with an output shaft of the combustion engine. The coupling means has a stiffness or rigidity which is selected in such a way that any axial, turning, wobbling (tilting) and/or flexing vibrations which are induced by the output shaft of the engine and would normally be transmitted to the friction clutch are damped and/or otherwise suppressed by the coupling means to an extent which ensures proper operation of the friction clutch, and especially proper operation of the adjusting unit.
The stiffness of the coupling means can be selected in such a way that the force to be applied to the actuating means for disengagement of the friction clutch is taken up by the coupling means without appreciable axial shifting of the clutch aggregate or assembly.
The adjusting unit of the just discussed aggregate or assembly can comprise resilient means in series with the at least one resilient device. Such aggregate or assembly can further comprise means for damping rotational and/or axial and/or radial vibrations of the counterpressure plate and such damping means is connectable between the output shaft of the engine and the counterpressure plate.
An additional feature of the invention resides in the provision of a driving unit, particularly for use in motor vehicles, which comprises an at least partially automatic (i.e., fully automatic or semiautomatic) transmission, an engine, and a torque transmitting friction clutch disposed between the engine and the transmission and being controlled at least in dependency on the operation of the transmission. The friction clutch of such driving unit comprises a pressure plate, a counterpressure plate (such as a flywheel) rotatable about a predetermined axis and connectable to the output shaft of the engine, means for non-rotatably connecting the pressure plate to the counterpressure plate with limited freedom of movement in the direction of the predetermined axis, a torque transmitting clutch disc between the two plates, at least one resilient device acting upon the pressure plate to bias the clutch disc against the counterpressure plate, friction linings forming part of the clutch disc and being engageable with and disengageable from at least one of the two plates and being subject to wear as a result of repeated engagement with and disengagement from the at least one plate, an adjusting unit including means for compensating at least for wear upon the friction linings to thereby maintain the bias of the at least one resilient device upon the pressure plate at a substantially constant value, means for engaging and disengaging the friction clutch including actuating means movable along a predetermined, path to engage and disengage the friction clutch, and torque varying means including means for gradually reducing the torque which can be transmitted by the friction clutch and/or by the clutch disc during a portion of movement of the actuating means along the predetermined path in a direction to disengage the friction clutch.
The at least one resilient device (e.g., a diaphragm spring) can have a degressive force-to-displacement ratio, at least during a portion of movement of the actuating means along the predetermined path in a direction to disengage the friction clutch.
The means for varying the torque which can be transmitted by the friction clutch can include means for reducing the transmittable torque during approximately 40-70 percent of movement of the actuating means along the predetermined path in a direction to disengage the friction clutch and for gradually increasing the torque which can be transmitted by the friction clutch during approximately 40-70 percent of movement of the actuating means along the path in a direction to engage the friction clutch.
The novel features which are considered as characteristic of the invention are set forth in particular in the appended claims. The improved friction clutch itself, however, both as to its construction and its mode of operation, together with additional features and advantages thereof will be best understood upon perusal of the following detailed description of certain presently preferred specific embodiments with reference to the accompanying drawings.